Sorting it out with Science
Separating Mixtures using Properties
Topics: Matter, Physical
Properties, Mixtures
Separate a mixture of several substances using physical properties.
Materials List
 Mixture of the
following materials:
iron filings, salt,
lentils (or similarly
sized objects), sand
 Preforms with popup caps
 Cups
 Magnet wand
 Small zip-loc
baggie
 Craft stick
 Warm water
This activity can be used
to teach:
Next Generation Science
Standards:
 Property of materials
(Grade 2, Physical
Science, 1-1; Grade 5,
Physical Science, 1-3)
 Structure of matter
(Grade 5, Physical
Science, 1-1)
 Mixtures (Grade 5,
Physical Science, 1-4)
 Chemical reactions
(Middle School,
Physical Science, 1-2)
 Science &
Engineering Practices
(grades 2-8)
To Do and Notice
1. Examine the mixture and note the variety of substances. Discuss some of the
visible properties of these substances (particle size, color, shape).
2. Note that all the largest objects (lentils) are the same. Begin by sorting out the
lentils using the pop-up cap as a sieve. Open the pop-up cap and shake the
smaller-sized particles into a cup. Set the separated “pure lentil” sample aside.
3. Sort the iron filings from the remaining mixture using the property of attraction to
magnets. Place a magnet wand into a baggie. Stir the mixture with the baggiecovered magnet and notice the accumulation of iron filings to the outside of the
baggie. Gently tap the magnet on the side of the cup to release any trapped sand
or salt particles.
4. Transfer the iron filings to an empty cup by holding the baggie over the cup and
removing the magnet wand from the baggie, releasing the iron filings.
5. Repeat steps 3 & 4 until all iron filings are removed. Set the separated “pure iron
filings” sample aside.
6. Sort the sand and salt by using salt’s property of high solubility in water. Pour
warm water into the mixture and stir until all the salt has dissolved, and then pour
the saltwater into a cup (note: the salt will not be a pure sample until the water
has evaporated.)
The Science Behind the Activity
Scientists can identify any substance using its unique set of physical and chemical
properties. All objects have 4 properties: Volume, Mass, Weight, and Density.
Volume measures the amount of space taken up by an object, mass measures the
amount of matter in an object, density measures how tightly packed the matter is in an
object, and weight is determined by the object’s position in space (accounting for
gravity.) Substances also exhibit other properties that can be used for identification,
such as attraction to magnets, crystalline structure, volatility, and solubility. These all
represent physical properties of matter; after a physical change, the substance is still
the same. Chemical properties include a substance’s ability to burn or react with an
acid; after a chemical change, a new substance is present. For example, if a craft stick
is broken into 2 pieces, its volume has changed, but it is still wood (physical change);
if the same craft stick is burned, a new substance is created and the stick is now
charcoal (chemical change.)
Scientists classify matter into either pure substances or mixtures. Mixtures can be
evenly mixed throughout (homogeneous) or unevenly mixed (heterogeneous).
Scientists use properties of matter to sort mixtures, just as students did in this activity.
Density, for example, is used in industry to separate recyclables and refine crude oil.
Web Resources (Visit www.raft.net/raft-idea?isid=395 for more resources!)
Developed and written by Coral Clark (RAFT)
Copyright 2014, RAFT